Water environment

About: Water environment is a research topic. Over the lifetime, 13384 publications have been published within this topic receiving 125138 citations.

Metabolism and toxicity of ammonia.

Abstract: THE recent and continuing interest in the possible toxic effects of ammonia in diseases of the liver and portal circulation has led to this progress report, which must of necessity begin with the origin of the problem. Ammonia is a highly toxic substance, and since it is a by-product of various phases of protein metabolism, mechanisms are required for its detoxification and disposal. In vertebrates existing in a water environment, this problem is handled very easily by a simple diffusion of ammonia into the surrounding fluid environment. The adaptation to a terrestrial environment, however, requires the conversion to a nontoxic . . .

The development and influence of gas bubbles in phreatic aquifers under natural flow conditions

Abstract: In a phreatic aquifer, bubbles may result from the entrapment of air during groundwater recharge and/or bacterial metabolism. The calculated critical depth of about 1 m at which bubbles are most likely to be found in a granular aquifer, coincides with the depth of 0.60 m of an almost stagnant water layer (specific discharge 1 × 10-6 cm sec-1) found at the water table region under natural flow conditions. Bubbles clog pores and therefore reduce the hydraulic conductivity without significantly reducing the volumetric water content. Stagnation at the water table region results since prevailing pressures (in the order of 10-1 atmospheres) are not sufficiently large to move bubbles through porous media in a water environment.

The ecotoxicity of graphene family materials: current status, knowledge gaps and future needs

Abstract: Recently, graphene family materials (GFMs) have been introduced among all fields of science and still get numerous attention. Also, the applicability of these materials in many areas makes them very attractive. GFMs have attracted both academic and industrial interest as they can produce a dramatic improvement in materials properties at very low filler content. The aim of this review is to identify, summarize, and present the first available information on the influence of GFMs on soil and water environment as well as identify the knowledge gaps and indicate the directions for the next generation of the original scientific investigations. The paper also presents our first preliminary impact assessment and potential pathways of GFMs distribution in the environment. We used as an example the reduced graphene oxide/Al2O3 nanocomposite (RGO/Al2O3) that has been previously designed and synthesized by us. Authors believe that further work should focus on improvement of characterization methodology applicable for ecotoxicity analyses and possible interactions between GFMs and different living ecosystems. Consequently, the potential impact of graphene and its derivatives on environmental health is a matter of academic interest. However, potential hazards sufficient for risk assessment and concerned with GFMs usage in consumer products first need to be investigated and identified. Further research should focus on gathering knowledge on GFMs properties for life cycle analyses, which still poses a great challenge for scientists.

Interdecadal change in the upper water column environment and spring diatom community structure in the Japan Sea: an early summer hypothesis

Abstract: Diatom community structure in the offshore Tsushima Current area of the Japan Sea was studied from 1972 to 1999 in relation to temporal variability of the upper water environment. We observed a distinct change in the community structure in spring during the 1980s, the period after the 1976/77 climate regime shift which has been reported to occur in the vast areas of the North Pacific. Chlorophyll a (chl a) concentration and chl a per cell were markedly low, and summer species includ- ing Pseudonitzschia spp. dominated the diatom community in spring during the 1980s. Mixed layer phosphate concentrations during the 1980s were lower in spring compared to the1970s and 1990s, suggesting that nutrient depletion to levels limiting diatom growth might occur early. This change seemed subsequently to cause a shift in the dominant diatom species from those adapted to eutrophic conditions to those adapted to oligotrophic conditions. Density profiles between the surface and 300 m showed the thickness of the surface Tsushima Current water and the cold subsurface water decreasing and increasing, respectively, from the late 1970s to the late 1980s. In addition, spring solar radiation increased during the 1980s. These conditions indicate intensified stratification of the upper water column. Increases in the phosphate gradient between the surface and subsurface layers sug- gested that the intensified stratification reduced nutrient supply to the surface and may be responsi- ble for early formation of the summer-like oligotrophic conditions. Based on these results, we propose the 'early summer hypothesis' as the cause of the apparent decline of the spring phytoplankton bio- mass in the Japan Sea during the 1980s.